A refrigerant compression type refrigeration cycle includes a compressor, a condenser, an expansion apparatus and an evaporator which are connected by a refrigerant pipe of a closed curve, and a refrigerant compressed in the compressor then circulates sequentially via the condenser, the expansion apparatus and the evaporator.
The compressor requires a predetermined amount of oil for lubrication of a driving unit, sealing and cooling of a compression unit, and the like. Therefore, a predetermined amount of oil has to be stored in a shell of the compressor. However, such oil is partially discharged from the compressor in a mixed state with a refrigerant, and then circulates together with the refrigerant via the condenser, the expansion apparatus and the evaporator. Here, if an excessive amount of oil circulates in the refrigeration cycle or a large amount of oil remains in the refrigeration cycle without being recollected into the compressor, oil deficiency inside the compressor is caused. This may lower reliability of the compressor and the refrigeration cycle may have a lowered heat exchange performance.
In order to solve these problems, the applicant of this application has introduced a technology, in Korean Patent Application No. 10-2008-0070335, filed on Jul. 18, 2008, titled “Hermetic compressor and refrigeration cycle apparatus having the same” that an oil separator is installed at a discharge side of the compressor, an oil pump is installed to recollect oil separated in the oil separator, and the oil separator and the oil pump are connected via an oil recollecting pipe. Accordingly, even if an inner space of the shell is filled with discharge pressure, the oil separated in the oil separator can be smoothly recollected. However, in the previously filed “compressor”, the oil pump is installed at a lower end of a crankshaft, which causes a pumping force to be deficient during low-speed driving of the compressor, which might have a problem of lowering reliability of the compressor.
There has been introduced a technology using differential pressure as a solution for constantly maintaining an amount of pumped oil even during low-speed driving of the compressor. Patent Application Laid Open No. U.S. 2005/0220652, filed on Oct. 6, 2005, titled Compressor has introduced a technology in which a differential pressure generating hole is formed through an orbiting scroll to communicate an inner space of a shell as a high pressure part with a suction groove (more concretely, a thrust bearing surface between scrolls) as a low pressure part, such that oil can be pumped by an attractive force generated due to a pumping force of an oil pump and pressure difference, thereby allowing the oil to be smoothly pumped up even during low-speed driving of the compressor, which results in improved reliability of the compressor.
The oil pumping technology using the attractive force generated due to the pumping force of the oil pump and the pressure difference in the related art allows oil to be smoothly supplied into the compression unit even during the low-speed operation by virtue of high pressure difference between the inner space of the shell and the suction groove, thereby preventing compression loss or damage of the compressor due to oil deficiency.